If all else fails then you could always try good old fashioned bleach. While it’s super effective at cleaning grout, there’s a good chance that it may damage certain tiles. We usually advise only using this method on white tiles, like the ones you may find in your bathroom (and particularly when the grout it white too).

If you’re going to clean grout with bleach, it’s a good idea to test it out on a small patch that is generally out of sight so you can check for colourfastness. It’s also a good idea to use gloves and wear old clothes as you may end up getting some bleach on them if you’re not careful. 

Step 1: Prepare the Area
Using the same method described above, prepare the area for deep cleaning.

Step 2: Apply the Bleach
Pour or spray the bleach onto the grout lines, making sure that you apply enough to fully cover all of the grout. Just do one section at a time to avoid getting bleach on your clothes and ruining them. Allow the bleach a few minutes to soak in and then get to work. 

Step 3: Brush the Bleach into the Grout
Using a nylon bristled brush, work the bleach into the grout. Scrub back and forth along the grout lines. Make sure you get the corners where dirt is most likely to accumulate. 

Step 4: Apply More Bleach Where Necessary
For tough to clean spots, apply more bleach or dip the scrubbing brush into a glass of bleach and scrub again. More bleach = more cleaning power. 

Step 5: Rinse the Floor
Using warm water, wipe or mop up the the bleach. Make sure that you do this thoroughly as any bleach left over will get into your socks and could get transferred into your carpets, which would be a disaster!